This invention relates to photoconductor drums having inserts to prevent noise caused by the drum as it is charged by contact with a member carrying an alternating current and/or is in contact with a cleaner blade. More specifically, this invention relates to efficient fabrication of such inserts.
Photoconductor drums typically comprise an aluminum tube coated with various materials to form a stable, photoconductive outer surface. The drums are charged in various ways, but a preferred charging technique to minimize ozone production is to contact the drum with a roller or other contacting member which carries an alternating electrical potential (AC) superimposed or a constant level potential (DC). The drum tends to react to the electrical influence of the AC signal by vibrating at a frequency twice that of the AC signal, and the sound of such vibration can be loud and shrill. It is also known that a flexible cleaner blade in contact with the drum may impart higher frequency acoustic noise to the drum.
To reduce such vibrations and eliminate or minimize the noise made by them, it is known to add weights to the inside of the drum. Various weights have been used. Often the weights are elastic in nature. However, solid weights are also used and are effective. This invention in the preferred form described employs solid weights closely similar to those which have been used commercially since 1998, with the addition of a flange which makes possible one-step molding of the weights. The weights are in the general shape of a capital letter xe2x80x9cCxe2x80x9d to facilitate insertion in the drum. U.S. Pat. No. 5,991,573 to Nohsho et al. and U.S. Pat. No. 5,960,236 to Zaman et al. disclose such a shape in photoconductive drum inserts.
The inserts of this invention can be made in an efficient single molding operation by the addition of a connection or bridge internal of the insert between two sides opposite the opening of the otherwise-generally-circular insert. The bridge makes it possible to simply remove the insert from its mold and let it cool unaltered. Without the bridge the insert would lose its shape during cooling.
Apparently to avoid the loss of shape, the prior, commercially-sold inserts mentioned in the foregoing where made as closed circles and then an opening was machined along the length of the insert to form the final xe2x80x9cCxe2x80x9d shape.
The inserts of this invention when molded are designed in width and length for insert in a predetermined photoconductor drum. However, they may be of various sizes to individually fit wide range of drums, so long as the drums have a hollow internal core into which the inserts may be placed. Placement is by squeezing the insert so that it collapses slightly toward its circumferential opening, moving the insert laterally into the hollow core of the drum, and then releasing the insert inside the drum.